A case report published Thursday in the journal BMJ Case Reports describes an 80-year-old woman in the U.K. whose lung tumor shrank by 76% between June 2018 and February 2021, a period during which she declined conventional treatment and instead self-administered CBD oil. The three physicians who authored the report say they cannot prove the oil caused the regression, but they suggest the case warrants further investigation.
The woman, who smoked about a pack of cigarettes per week, was diagnosed with lung cancer in June 2018. She refused treatment after witnessing the side effects her husband endured during radiotherapy. Acting on a relative's advice, she began taking roughly 0.5 milliliters of CBD oil two to three times daily. By February 2021, imaging showed her tumor had shrunk by more than three-quarters, a change the doctors describe as both remarkable and puzzling.
While the doctors were able to obtain laboratory details on the oil's THC, CBD, and THCA content, they wrote that they cannot identify which ingredient—if any—contributed to the regression. They emphasized that correlation does not equal causation, and that a single anecdotal case cannot establish a medical effect.
“We are unable to confirm the full ingredients of the CBD oil that the patient was taking or to provide information on which of the ingredient(s) may be contributing to the observed tumor regression,” the authors wrote in the paper. They also noted, “Although there appears to be a relationship between the intake of CBD oil and the observed tumor regression, we are unable to conclusively confirm that the tumor regression is due to the patient taking CBD oil.”
The case adds to a growing body of anecdotal reports about CBD's potential health effects, but experts caution that such evidence is far from conclusive. The authors themselves call for robust, large-scale clinical trials to determine whether cannabinoids have any real anti-cancer properties. “More research is needed to identify the actual mechanism of action, administration pathways, safe dosages, its effects on different types of cancer and any potential adverse side effects when using cannabinoids,” they concluded.
While this report does not prove that CBD oil can treat cancer, it highlights the need for rigorous scientific inquiry into a compound that many patients already use without medical supervision. The case also underscores the importance of patient-reported outcomes in generating hypotheses for future research.
